Deep trenches, typically having a depth exceeding 1 micron in contrast to shallow trenches having a depth less than 1 micron, are employed in the semiconductor industry to provide a variety of useful devices including a deep trench capacitor. The deep trenches may be utilized in a stand-alone semiconductor circuit such as a dynamic random access memory (DRAM) circuit to provide deep trench capacitors, or may be utilized as an embedded circuit component of a semiconductor chip that also includes other semiconductor circuits such as a processor core or other logic circuits. Particularly, embedded capacitors employing a deep trench are employed to enable an embedded memory device, e.g., an embedded dynamic random access memory (eDRAM) cell, a passive component of a radio frequency (RF) circuit, and decoupling capacitors that provide a stable voltage supply in a semiconductor circuit.
Semiconductor-on-insulator (SOI) substrates are employed in the semiconductor industry for performance benefits due to reduced capacitive coupling between semiconductor devices and the bulk portion of the substrate provided by a buried insulator layer. High performance logic chips are frequently manufactured on an SOI substrate to provide enhanced performance over devices having comparable dimensions and manufactured on a bulk substrate. Incorporation of embedded capacitors into the SOI substrate, however, requires not only formation of deep trenches in the SOI substrate but also formation of a buried plate beneath a buried insulator layer, while preventing diffusion of dopants into a top semiconductor layer above the buried insulator layer.
In one prior art method, a doped silicate glass such as an arsenosilicate glass (ASG) layer is formed within a deep trench. The portion of the ASG layer above a top surface of the buried insulator layer is removed, which is followed by a drive-in anneal that diffuses arsenic into the handle substrate beneath the buried insulator layer to form a buried plate. The ASG layer is subsequently removed. Multiple processing steps employed in this prior art method incur significant cost and require considerable processing time.
In view of the above, there exists a need for methods of manufacturing a deep trench capacitor employing a more economical and less time consuming process sequence, and semiconductor structures enabling such a processing sequence.